AB0376 DIFFERENCES IN IMMUNOGLOBULIN LEVELS IN PATIENTS WITH ANCA-ASSOCIATED VASCULITIS AND RHEUMATOID ARTHRITIS TREATED WITH RITUXIMAB
Authors: M. Sanz, C. M. Oñoro López, G. Bonilla, D. Peiteado, A. Noblejas Mozo, Á. Robles Marhuenda, J. J. Rios, D. Benavent, C. Plasencia, L. Nuño, I. Monjo, A. Villalba, A. Balsa
Journal: Annals of the Rheumatic Diseases (2022)

Background Hypogammaglobulinemia (HGGS) is one of the adverse effects of Rituximab (RTX), a chimeric monoclonal antibody directed against the CD20 receptor, frequently observed in ANCA-associated vasculitis (AAV) patients. Objectives To study the characteristics of patients with AAV on RTX treatment and to analyze the factors associated with HGGS, as well as to compare them with patients with rheumatoid arthritis (RA) on the same treatment. Methods Retrospective descriptive study of patients with a diagnosis of AAV or RA treated with RTX who had immunoglobulin levels prior to treatment and after each cycle were included. Demographic, clinical and analytical variables were analyzed. Patients who developed HGGS versus those who did not were compared using Student’s t and Mann-Whitney U for continuous variables and chi-square for categorical variables. Results Ninety-five patients were included, 19 (20%) with AAV and 76 (80%) with RA. Of the 34 (35.8%) who developed HGGS, 19 had RA (25%) and 15 AAV (79%) (p&lt;0.001). The 6 patients who presented with severe HGGS (IgG&lt;500) belonged to the AAV group. The overall sample was divided into patients with HGGS and patients without (Table 1). Significant differences were obtained in relation to diagnosis (p&lt;0.001), age at diagnosis and at the start of treatment, being higher in patients with HGGS (p 0.005 and p 0.001) and years of disease evolution (p 0.036). Patients with HGGS had a lower mean baseline IgG (p&lt;0.001). The HGGS group had more severe infections (infections requiring admission) (p 0.005) and the time from RTX administration to the development of infection was shorter in this group (p 0.017). The frequency of abdominal infection was higher in the HGGS group (p 0.050), and there were no significant differences with the other types of infection. Table 1. Total sample (n= 95) HGGS IgG (n= 34) No HGGS IgG (n= 61) P Women n/N(%) 70/95(73.7) 23/34(67.6) 47/61(77) 0.318 Age (m±SD) 64±12 68±10 62±12 0.005 Age at start of treatment (m±SD) 57±12 62±10 54±12 0.001 Years of evolution (m±SD) 11±9 8±9 12±10 0.036 RA n/N(%) 76/95(80) 19/34(55.9) 57/61(93.4) &lt;0.001 AAV n/N(%) 19/95(20) 15/34(44.1) 4/61(6.6) &lt;0.001 Glomerular filtration rate &lt;60 n/N(%) 7/91(7.7) 4/34(11.8) 3/61(4.9) 0.164 GCS AD in the previous year (m±SD) 2918±3102 3265±3050 2690±3155 0.238 GC AD during treatment (m±SD) 4656±17713 2889±2778 5576±21775 0.271 Total GC AD (m±SD) 56411±326716 117050±484186 5879±6089 0.159 CFM AD (m±SD) 0.51±2.25 1.1±3.1 0.2±1.5 0.032 Baseline IgG (m±SD) 1107±340 933±346 1203±297 &lt;0.001 Infection n/N(%) 58/95(61.1) 23/34(67.6) 35/61(57.3) 0.325 Severe infection n/N(%) 19/95(20) 12/34(35.3) 7/61(11.5) 0.005 Time to infection (months)(m±SD) 43±43 30±36 57±45 0.017 Exitus n/N(%) 8/95(8.4) 2/34(5.9) 6/61(9.9) 0.270 Conclusion A significantly higher percentage of HGGS is observed in patients with AAV treated with RTX compared to patients with RA. The development of HGGS seems to be influenced by age at diagnosis and at the start of treatment, years of disease evolution and low levels of IgGs prior to the start of treatment. In addition, there is a higher frequency of severe infections in the HGGS group. Studies with larger sample sizes are needed to confirm these results. References [1]Roberts DM, Jones RB, Smith RM, Alberici F, Kumaratne DS, Burns S, Jayne DR. Rituximab-associated hypogammaglobulinemia: incidence, predictors and outcomes in patients with multi-system autoimmune disease. J Autoimmun. 2015 Feb;57:60-5. doi: 10.1016/j.jaut.2014.11.009. Disclosure of Interests None declared